The present invention relates to a radial rotary transmission leadthrough with a rotating shaft which has at least two substantially axially running channels which have radial transition openings open to the periphery of the shaft, and with at least one guide bush tightly surrounding the shaft in the area of the transition openings which has at least one radial feed bore each for every one of the channels to be connected via the bush, wherein the different channels have their radial transition openings at different axial positions of the shafts.
Radial rotary transmission leadthroughs of this type have already been long known.
The corresponding radial feed bores in the bush lie on the same axial position as a radial transition opening of that channel in the shaft with which the feed bore concerned is to be connected. In this way a gas or a liquid can be introduced via the feed bore and the radial transition opening into the concerned channel of the shaft or conversely a corresponding fluid can pass out of the channel of the shaft via the transition opening into the feed bore and from there into the associated external fluid system.
Corresponding channels and feed bores are very frequently needed to operate, at one end of the shaft, hydraulically actuatable elements connected to the former, by supplying or removing corresponding hydraulic fluid under pressure. Expediently, there is provided in each case, at axial height of a pair of feed openings each consisting of the corresponding feed bore and the radial transition opening of the channel in the shaft, an encircling groove in the area of the sealing faces between shaft and bush, with the result that, regardless of the relative rotation position of the transition opening in respect of the feed bore fluid can be continuously fed into the channel or removed from the channel. To separate the different channels, it is accordingly imperative that the different feed bores and also the different transition openings of the different channels are spaced apart from one another in axial direction.
The channels extend substantially in axial direction through the shaft, wherein these can optionally be annular channels lying around a central channel and/or concentrically around the centre, but optionally also corresponding axial bores can be provided in the shaft which, depending on the length of the shaft, are either created directly by bores or e.g. by having the shaft composed of a core and a sleeve or a central tube and an outer tube, wherein corresponding grooves are cut into the outer wall of the inner core or tube and/or into the inner wall of the outer tube (which have the same diameter), which form a corresponding axial channel after the two parts have been put together.
From time to time, several such rotary transmission leadthroughs are placed axially one behind the other at a shaft which has the matching radial feed bores and transition openings at the respective positions of these rotary transmission leadthroughs. Alternatively, several transition bores can be provided at different axial positions in a bush. However, a group of rotary transmission leadthroughs arranged axially behind one another requires a relatively long section of the shaft. On the other hand, a rotary transmission leadthrough with one bush with a plurality of radial feed bores, though shorter, still has a considerable axial length, as each of the channels requires a certain axial space because the transition openings and the corresponding feed bores of different channels must each lie at a different axial position and because the grooves of respective neighbouring channels/feed bores are generally also to be separated from one another by an axially sufficiently long section of a sealing face. It is understood that, for this, the inner surface of the bush must be in relatively tight sliding engagement with the outer surface of the shaft, wherein within the framework of the present description these sections of bush and shaft are called sealing faces. These sealing faces are cylindrical inner and outer surfaces respectively with virtually the same diameter, with the result that they can slide directly on one another if one of the two parts rotates relative to the other, wherein in general the shaft is formed as the rotating machine part. However, in principle the shaft could also be connected to a stationary machine part, while the bush would be connected to a rotating machine part, wherein in this case, however, the axial channels should be arranged in the bush and the radial feed bores would have to be arranged in the shaft, which would then expediently be a hollow shaft.
It is understood that when there is a large number of channels and a correspondingly large number of transition openings and feed bores the axial length of the bush must also be correspondingly large, and that it is generally difficult to provide two components with constantly equal diameters over a relatively great axial length, with the result that the thus-produced sealing faces form only a very narrow sealing gap and e.g. slide over a film, conveyed from the channels or feed bores, made of a fluid, without the friction between bush and shaft becoming too great and bringing about a possibly excessive heating of the sealing ring faces and also the surroundings including the fluids to be passed though. However, the sealing gap is to be kept as small as possible, in order that the otherwise unavoidable leakage rates are as small as possible and also fluids from different channels do not mix with one another, nor must there be a reciprocal pressurization of neighbouring channels.
In general, a corresponding bush for equalizing any tolerances of the sealing faces is housed “floating”. i.e. it is housed such that it receives an (albeit small) radial and axial movement margin. However, tolerance deviations of the sealing faces which require a corresponding radial movement space inevitably also mean that the play or the seal gap between the sealing faces is relatively large in places, with the result that the leakage rates are also accordingly greater. Too great an axial movement margin can cause the bush to tilt or tip, with the result that diagonally opposite inner edges of the bush come into too strong a frictional engagement with the shaft, whereby the shaft can jam in the bush in unfavourable circumstances.